The Van de Graaff Generator, 1933

MIT has a long history of energy research. The photograph reproduced here is a 1933 time-lapse image of the “flash-over” emitted by MIT's High-Voltage Generator at Round Hill a few weeks after it first became operational. Known colloquially as the “Van de Graaff Generator,” the apparatus was designed to supply high voltage to accelerate subatomic particles to very high velocities for the bombardment and study of atomic nuclei. It also had important applications in clinical research.

President Karl T. Compton brought Robert J. Van de Graaff to MIT from Princeton in 1931 to bolster the Institute's physics department and develop a much-needed facility for high-voltage research. A conveniently large airship hangar on the estate (“Round Hill” in South Dartmouth, Mass.) of Colonel E. H. R. Green, an MIT benefactor with a strong interest in science, radio, aeronautics, and engineering, provided a home for the oversized equipment. Work on experimental models proceeded by stages until the full-scale apparatus was ready. On December 12, 1933, MIT issued a “Progress Report on the M.I.T. High-Voltage Generator at Round Hill” detailing tests and modifications, incorporating striking photos of the equipment in action, and making predictions about its “unequalled power” for generating direct current.

The apparatus, standing about 40 feet high, consisted of two empty metal spheres on top of two textolite columns mounted on trucks, which could be moved on rails for experiments either inside or outside the hangar. Electrostatic charge was brought up to the hollow spheres after being carried from ground by means of long, four-foot-wide paper insulating belts on steel pulleys rotating at 3600 RPM. Collectors inside each sphere transferred the charge to the outer surface. Refinements included various devices such as felt gaskets and dehumidifiers to create conditions for greater efficiency. The generator was capable of operating at 5,000,000 volts. After it became obsolete it was relocated to the Museum of Science in Boston, where it remains on permanent exhibit.